Legend:

1. Obtain DEM data. ASTER should be used in preference to SRTM unless there is a good reason not to.

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* ASTER from http://asterweb.jpl.nasa.gov/gdem-wist.asp. You will need to register, define the search area you're interested in and create an appropriate data order.

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===Please use username: arsf password: ArsfPr0cess

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* SRTM from http://earthexplorer.usgs.gov. Expand the "Digital Elevation" link on the left and tick the box labelled "SRTM". Enter bounding co-ordinates for the area you want data for, clicking the green "+" icon after each one. Note that this currently seems not to always work correctly for locations in DMS format (at least in Firefox), you may need to switch to decimal degrees (which work fine). Click on the "Search" button in the bottom-right, and you should be presented with a list of items matching your search (there should be only one thing in it). Click on the "SRTM" link (you may need to enable pop-ups if you've got them blocked), and you will be presented with a list of matching SRTM tiles and download links - download the data you want to use. Note that only SRTM 3-arc-second resolution data is available for sites outside North America. For sites in North America higher resolution data can be obtained via the USGS [http://seamless.usgs.gov/ Seamless Server]